Human cytomegalovirus (CMV) has an intimate relationship with its human host and disease is tightly linked to the immune status of infected persons. An understanding of how CMV induces host immunity is of critical importance in efforts to combat CMV disease. The long-term goal of this research is to develop an understanding of the mechanism by which CMV activates innate immune responses. Inflammatory cytokines and activation of the antiviral activities driven by type I interferon are hallmarks of innate immunity and serve critical roles in promoting an adaptive response and in temporarily slowing the pathogen. Several lines of evidence have raised awareness that CMV activates innate immune responses at the earliest stage of infection, during the entry process. We recently discovered that a member of the Toll like receptor (TLR) family (TLR2) detects CMV. TLR2 sensing of CMV leads to activation of a NF-kappaB dependent signal transduction pathway and to synthesis of inflammatory cytokines. TLRs are ancient, evolutionarily conserved pattern recognition receptors that detect a wide range of microbial pathogens. This exciting new knowledge provides a significant opportunity to learn about the molecular basis by which these primordial immune sensors detect viral pathogens as well as elucidate the cellular machinery involved in the downstream transcription induction. The first aim of our proposal will further characterize the role of TLR2 in CMV activation of inflammation. In addition, we will identify the TLR2 associating partner (TLR1 or TLR6) as well as the primary cytoplasmic signaling adaptor proteins in the pathway. Aim 2 will examine a mechanistic link between TLR2 and the induction of the interferon pathway. The role of a newly discovered cytoplasmic adaptor, TICAM which has been shown to interact with TLR2 and to activate interferon regulatory factor 3 (IRF-3), will be tested for involvement in the CMV pathway. Aim 3 will build on exciting new preliminary data that show the CMV envelope glycoprotein B (gB) can physically associate with TLR2. In addition, we show that gB has the intrinsic ability to activate cytokine induction in a TLR2 dependent manner. Detailed structure/ function analysis will be conducted in efforts to understand the molecular pattern displayed by gB. Lastly we will move the work into pathogenesis-oriented research. Innate immune responses will be characterized in cell types critical to CMV pathogenesis, such as endothelial cells and monocyte/macrophages.